BOSTON, Jan. 21--Virgil Akins knocked weary Tony DeMarco into virtual fistic obscurity tonight with a 12th round technical knockout in a brutal rematch of welterweights at Boston Garden.

Akins, the church deacon from St. Louis who waited for the Boston battler to punch himself out, finished the bout with a jarring right uppercut and Referee Eddie Bradley stepped in to call a halt at 1:53 of the round.

DeMarco had been down once in the eighth round and twice in the 11th, but didn't know how to quit until Bradley made the decision for him before an overflow crowd of some 15,000 screaming fans.

The victory in this Massachusetts version of the welterweight championship which Akins had won in this same ring last October put Virgil very much in the National Boxing Assn. Welter plans.

The NBA plans to pit Akins against the winner of the coming Isaac Logart-Vince Martinez fight for the welter crown.

DeMarco, his right eye encircled with blood from a cut which was opened in the ninth round, spun helplessly into the ropes from the finishing Akins uppercut.

Virgil, 29-year-old master of the waiting game, had landed several damaging blows to the midsection prior to the last shot.

But it was an accumulation of Akins' punches and DeMarco's arm weariness as a result of his all-out effort which paved the way for the outcome.

Akins, who slipped to the canvas in the fourth when hurt by a left hook, sent Tony down with a right uppercut and two violent lefts in the eighth. DeMarco fell against the ropes and pitched forward on his stomach. He was up at the count of seven and gamely finished the round by holding his own in a slugfest.

In the ninth, Akins opened the cut over Tony's eye, though DeMarco had the better of the punching.

Akins hurt DeMarco with an uppercut as the 10th round got underway and pounded the 26-year-old local boy unmercifully. However, the remarkable punishment-taker from nearby Fleet St. landed seven straight shots to the head just before the bell.

Akins landed a left to the body and a followup left to the head which staggered DeMarco backward into a sitting position in the 11th. He got up at three.

Another left to the body by Akins buckled DeMarco forward to his knees and he was wobbling as the bell rang.

The fight was a "must" for DeMarco, who was knocked out by Akins Oct. 29 in the 14th round. Tony had been world welter king in 1955, but lost by knockouts to Carmen Basilio in a title defense and a later rematch.